1. Technical Field
The present invention relates to a manufacturing method of a semiconductor device manufacturing the semiconductor device of an integrated circuit, etc, on a substrate, for processing a substrate such as a semiconductor silicon wafer, and a substrate processing apparatus, and particularly, relates to removing a natural oxide film and a contaminated matter such as an organic contamination on a substrate surface, and growing a good epitaxial film on the substrate surface, and further specifically relates to a technique of forming a high quality interface between a semiconductor substrate and the epitaxial film.
2. Background Art
In a silicon surface and a substrate having an insulating film such as a silicon nitride film, a technique of selectively growing a film only on a silicon surface is called a selective growth.
A finer MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) with higher performance has been progressed. However, as shown in FIG. 4A, source/drain of the MOSFET has problems such as lowering of a contact resistance and a growth of the epitaxial layer with defect density suppressed to minimum. A method of selectively growing a silicon epitaxial film on the source/drain is given as one of the methods of solving the aforementioned problems. A method of partially exposing an Si substrate between inter-layer insulating films, and selectively growing the silicon epitaxial film thereon, is given as a method of lowering the contact resistance, other than lowering of the contact resistance of the source/drain.
In recent years, in order to solve a problem such as increasing the natural oxide film at the time of introducing the substrate into a processing furnace or deterioration of a semiconductor due to adhesion of impurities, a vertical type pressure reducing CVD apparatus having an anterior chamber provided in the processing furnace is used. In this apparatus, a method of removing oxygen or moisture, etc, in the front chamber down to 1 ppm or less, and after nitrogen substitution, introducing the substrate into the processing furnace is used. An unprocessed substrate is transferred to a processing furnace anterior chamber from a substrate carrying port, and is set in a jig (boat) for substrate processing. The processing furnace anterior chamber is formed in a sealed structure possible to be evacuated, and by repeating evacuation and nitrogen-purging, the oxygen and the moisture are sufficiently removed, and thereafter, the substrate is introduced into the processing furnace. A drive axial part, a boat rotation mechanism part, and a wiring part for introducing the substrate and the jig for substrate processing are set in an inside of the processing furnace anterior chamber, thus involving a problem of contamination on the substrate surface due to an organic matter when evacuation is performed.
In addition, the processing furnace in the aforementioned apparatus has a double structure made up of an inner tube and an outer tube. Carrier gas and reactive gas are introduced from a furnace throat opening at a relatively low temperature, passes through the inner tube to process the substrate, then passes between the outer tube and the inner tube and is exhausted. This processing furnace has an advantage that by changing a diameter of the inner tube, a vapor phase reaction can be suppressed, thus facilitating a maintenance. However, there is a problem of contamination on the substrate surface due to the organic matter from the boat rotation mechanism part and an O-ring part.
The silicon substrate is loaded into the apparatus after pre-cleaning it by using dilute hydrofluoric acid, etc. However, the natural oxide film and the impurities on the substrate must be removed before the selective growth processing, after the substrate is introduced into the processing furnace.
When a semiconductor silicon wafer is exposed to atmospheric air, silicon on a wafer surface reacts with the oxygen in the atmospheric air, to form the natural oxide film with a thickness of about several Å. Such a natural oxide film acts not only as a defect element in a wiring step of an integrated circuit, but also as a cause of increasing the contact resistance, which causes an obstacle to the operation speed and reliability of the integrated circuit.
Conventionally, in order to remove this natural oxide film, the wafer must be subjected to annealing process by flowing hydrogen gas at a high temperature (about 800° C.). However, problems such as thermal damage to a substrate element and increase of thermal budget have been more serious. Therefore, the temperature of the substrate processing needs to be decreased, thus requiring a method of removing the natural oxide film instead of a hydrogen annealing process at a high temperature, which is a conventional art.